Chemical Equilibrium MCQs 2026

Chemical equilibrium is reached when

1. AThe reaction has completely stopped✓
2. BAll reactants are converted to products✓
3. CThe rate of the forward reaction equals the rate of the reverse reaction✓
4. DOnly products remain in the system✓

Chemical equilibrium is described as

1. AStatic✓
2. BDynamic✓
3. CIrreversible✓
4. DPermanent✓

The equilibrium constant, Kc, is expressed in terms of

1. ARate constants only✓
2. BActivation energies✓
3. CMolar concentrations of products and reactants at equilibrium✓
4. DPressure of reactants only✓

A large value of the equilibrium constant (K >> 1) indicates that at equilibrium

1. AReactants are favored✓
2. BThe reaction has not started✓
3. CReactants and products are equal✓
4. DProducts are favored✓

A small value of the equilibrium constant (K << 1) indicates that at equilibrium

1. AProducts are favored✓
2. BReactants are favored✓
3. CThe reaction is at completion✓
4. DEquilibrium is not reached✓

Le Chatelier's principle states that if a system at equilibrium is disturbed, the system will shift to

1. AStop the reaction completely✓
2. BIncrease disorder indefinitely✓
3. CFavor the reactants always✓
4. DCounteract the disturbance and restore equilibrium✓

According to Le Chatelier's principle, increasing the pressure on a gaseous equilibrium favors the side with

1. AMore gas moles always✓
2. BEqual moles on both sides✓
3. CFewer gas moles✓
4. DNo gas molecules involved✓

For an exothermic reaction at equilibrium, increasing the temperature shifts equilibrium towards the

1. AProducts✓
2. BReactants✓
3. CNeither side✓
4. DDepends only on pressure✓

For an endothermic reaction at equilibrium, increasing the temperature shifts equilibrium towards the

1. AProducts✓
2. BReactants✓
3. CNeither side✓
4. DCatalyst side✓

Adding a catalyst to a reaction at equilibrium

1. AShifts equilibrium towards products✓
2. BShifts equilibrium towards reactants✓
3. CSpeeds up attainment of equilibrium without shifting its position✓
4. DChanges the value of Kc✓

The equilibrium constant Kp is related to Kc by the equation

1. AKp = Kc always✓
2. BKp = Kc / RT✓
3. CKp = Kc(RT)^Δn✓
4. DKp = Kc + Δn✓

In the Haber process (N2 + 3H2 ⇌ 2NH3), increasing pressure favors the formation of

1. AN2 and H2✓
2. BNH3 (fewer moles of gas)✓
3. CNo change✓
4. DEqual amounts of all species✓

The equilibrium constant of a reaction depends on

1. ATemperature only✓
2. BConcentration of reactants✓
3. CPressure only✓
4. DPresence of a catalyst✓

For a reaction at equilibrium, the reaction quotient Q equals K when

1. AThe system is at equilibrium✓
2. BThe reaction has not started✓
3. COnly products are present✓
4. DThe temperature changes✓

If Q < K for a reaction, the reaction will proceed in the

1. AReverse direction✓
2. BForward direction to reach equilibrium✓
3. CNo direction; it is already at equilibrium✓
4. DDirection that decreases products only✓

If Q > K for a reaction, the reaction will proceed in the

1. AForward direction✓
2. BNeither direction✓
3. CDirection of increasing volume✓
4. DReverse direction to reach equilibrium✓

Le Chatelier's principle states that if a system at equilibrium is disturbed, the system will shift to

1. AStop the reaction completely✓
2. BIncrease disorder indefinitely✓
3. CFavor the reactants always✓
4. DCounteract the disturbance and restore equilibrium✓

According to Le Chatelier's principle, increasing the pressure on a gaseous equilibrium favors the side with

1. AMore gas moles always✓
2. BEqual moles on both sides✓
3. CFewer gas moles✓
4. DNo gas molecules involved✓

For an exothermic reaction at equilibrium, increasing the temperature shifts equilibrium towards the

1. AProducts✓
2. BReactants✓
3. CNeither side✓
4. DDepends only on pressure✓

For an endothermic reaction at equilibrium, increasing the temperature shifts equilibrium towards the

1. AProducts✓
2. BReactants✓
3. CNeither side✓
4. DCatalyst side✓

Adding a catalyst to a reaction at equilibrium

1. AShifts equilibrium towards products✓
2. BShifts equilibrium towards reactants✓
3. CSpeeds up attainment of equilibrium without shifting its position✓
4. DChanges the value of Kc✓

The equilibrium constant Kp is related to Kc by the equation

1. AKp = Kc always✓
2. BKp = Kc / RT✓
3. CKp = Kc(RT)^Δn✓
4. DKp = Kc + Δn✓

In the Haber process (N2 + 3H2 ⇌ 2NH3), increasing pressure favors the formation of

1. AN2 and H2✓
2. BNH3 (fewer moles of gas)✓
3. CNo change✓
4. DEqual amounts of all species✓

The equilibrium constant of a reaction depends on

1. ATemperature only✓
2. BConcentration of reactants✓
3. CPressure only✓
4. DPresence of a catalyst✓

For a reaction at equilibrium, the reaction quotient Q equals K when

1. AThe system is at equilibrium✓
2. BThe reaction has not started✓
3. COnly products are present✓
4. DThe temperature changes✓

If Q < K for a reaction, the reaction will proceed in the

1. AReverse direction✓
2. BForward direction to reach equilibrium✓
3. CNo direction; it is already at equilibrium✓
4. DDirection that decreases products only✓

If Q > K for a reaction, the reaction will proceed in the

1. AForward direction✓
2. BNeither direction✓
3. CDirection of increasing volume✓
4. DReverse direction to reach equilibrium✓

Which type of equilibrium involves reactants and products in different physical states

1. AHomogeneous equilibrium✓
2. BStatic equilibrium✓
3. CHeterogeneous equilibrium✓
4. DDynamic imbalance✓

In a homogeneous equilibrium, all reactants and products are in the

1. ASame physical state/phase✓
2. BDifferent physical states✓
3. CSolid state only✓
4. DGaseous state only, never liquid✓

The equilibrium expression for a heterogeneous reaction does NOT include the concentration of

1. APure solids and liquids✓
2. BGases✓
3. CAqueous ions✓
4. DAll species equally✓

Which factor does NOT shift the position of a chemical equilibrium

1. APresence of a catalyst✓
2. BChange in concentration✓
3. CChange in temperature✓
4. DChange in pressure (for gaseous systems)✓

The solubility product (Ksp) is an equilibrium constant that applies to

1. AGaseous reactions only✓
2. BAcid-base neutralization✓
3. CRedox reactions only✓
4. DThe dissolution of a sparingly soluble ionic compound✓

If the ionic product of a salt solution exceeds its Ksp, the solution is

1. AUnsaturated✓
2. BDiluted✓
3. CAt equilibrium exactly✓
4. DSupersaturated, and precipitation occurs✓

The common ion effect refers to the decrease in solubility of a salt when

1. ATemperature is increased✓
2. BA common ion is added from another source✓
3. CThe solution is diluted✓
4. DA catalyst is added✓

Dynamic equilibrium means that at the macroscopic level properties remain constant while at the molecular level

1. AAll reactions have stopped✓
2. BOnly forward reaction continues✓
3. COnly reverse reaction continues✓
4. DForward and reverse reactions continue at equal rates✓

Which of the following statements about K (equilibrium constant) is true

1. AK changes when concentration changes✓
2. BK changes with a catalyst✓
3. CK is constant at a given temperature✓
4. DK is always greater than 1✓

For the reaction A ⇌ B, if K = 1, at equilibrium

1. A[A] = [B]✓
2. B[A] >> [B]✓
3. C[B] = 0✓
4. D[A] = 0✓

Removing a product from an equilibrium mixture will shift the equilibrium towards

1. AThe reactants✓
2. BNo change✓
3. CThe products (to replace what was removed)✓
4. DA new catalyst-based state✓

Adding more reactant to a system at equilibrium shifts the reaction towards

1. AThe reactants✓
2. BThe products✓
3. CNo change✓
4. DEquilibrium is destroyed permanently✓

Which of the following is an example of a reversible reaction commonly cited in equilibrium studies

1. AN2 + 3H2 ⇌ 2NH3 (Haber process)✓
2. BCombustion of magnesium✓
3. CNeutralization of a strong acid with a strong base✓
4. DPrecipitation of AgCl (considered irreversible in these contexts)✓

The contact process for manufacturing sulfuric acid involves the equilibrium

1. AN2 + 3H2 ⇌ 2NH3✓
2. B2SO2 + O2 ⇌ 2SO3✓
3. CCaCO3 ⇌ CaO + CO2✓
4. DH2 + I2 ⇌ 2HI✓

Increasing pressure has no effect on gaseous equilibria where

1. AReactant moles exceed product moles✓
2. BProduct moles exceed reactant moles✓
3. CThe reaction is exothermic✓
4. DThe number of gas moles is equal on both sides✓

The degree of dissociation of a weak electrolyte at equilibrium is affected by

1. ANothing at all✓
2. BOnly the container's shape✓
3. CCatalysts only✓
4. DDilution (per Ostwald's dilution law)✓

Ostwald's dilution law relates the degree of dissociation of a weak electrolyte to its

1. AMolar mass✓
2. BConcentration (dilution)✓
3. CColor✓
4. DBoiling point✓

Which of the following equilibria is heterogeneous

1. AN2(g) + 3H2(g) ⇌ 2NH3(g)✓
2. BH2(g) + I2(g) ⇌ 2HI(g)✓
3. C2SO2(g) + O2(g) ⇌ 2SO3(g)✓
4. DCaCO3(s) ⇌ CaO(s) + CO2(g)✓

For an equilibrium at constant temperature, changing the volume of the container affects

1. AK only, not the position✓
2. BNothing at all✓
3. COnly solid-state equilibria✓
4. DThe position of equilibrium, but not K, for gaseous reactions with unequal moles✓

The equilibrium constant expression is written using the

1. ACoefficients of reactants only✓
2. BRate law of the reaction✓
3. CActivation energy✓
4. DBalanced chemical equation's stoichiometric coefficients as exponents✓

Which condition favors maximum yield of ammonia in the Haber process according to Le Chatelier's principle

1. ALow pressure and high temperature✓
2. BHigh pressure and moderately low temperature✓
3. CLow pressure and low temperature✓
4. DHigh temperature and low pressure only✓

In practice, industrial processes like the Haber process use a compromise temperature to balance

1. AYield (favored by low T) and reaction rate (favored by high T)✓
2. BCost of catalyst and volume of reactor✓
3. CColor of product and purity✓
4. DPressure and humidity only✓

Which statement about reversible reactions is correct

1. AThey can proceed in both forward and backward directions✓
2. BThey go to completion in one direction only✓
3. CThey never reach equilibrium✓
4. DThey require a catalyst to be reversible✓

The equilibrium position of a weak acid dissociation in water is described by its

1. AAcid dissociation constant, Ka✓
2. BSolubility product, Ksp✓
3. CRate constant, k✓
4. DMolar mass✓

A high value of Ka for an acid indicates that the acid is

1. AWeak✓
2. BStrong (highly dissociated)✓
3. CNeutral✓
4. DNot soluble in water✓

The equilibrium constant for the reverse of a reaction is related to the equilibrium constant of the forward reaction (K) by

1. AKreverse = K✓
2. BKreverse = -K✓
3. CKreverse = K^2✓
4. DKreverse = 1/K✓

If the equilibrium constant of reaction 1 is K1 and reaction 2 is K2, and reaction 3 is the sum of reactions 1 and 2, then K3 equals

1. AK1 + K2✓
2. BK1 × K2✓
3. CK1 − K2✓
4. DK1 / K2✓

In a saturated solution of a sparingly soluble salt, the equilibrium exists between the

1. AGas and liquid phases only✓
2. BTwo different solutes✓
3. CUndissolved solid and its dissolved ions✓
4. DSolvent and container walls✓

The value of the equilibrium constant for a reaction at a fixed temperature is independent of

1. AThe initial concentrations of reactants and products✓
2. BTemperature✓
3. CThe nature of the reaction✓
4. DThe stoichiometry of the reaction✓

Which of the following would increase the rate of both forward and reverse reactions equally without shifting equilibrium

1. AIncreasing reactant concentration✓
2. BRemoving product✓
3. CAdding a catalyst✓
4. DIncreasing temperature✓

Equilibrium involving a solid and its saturated solution, such as sugar dissolving in water, is an example of

1. AChemical equilibrium only✓
2. BRedox equilibrium✓
3. CPhysical equilibrium✓
4. DNuclear equilibrium✓

For the equilibrium PCl5(g) ⇌ PCl3(g) + Cl2(g), decreasing the pressure will shift equilibrium towards

1. AThe products (more moles of gas)✓
2. BThe reactants (fewer moles of gas)✓
3. CNo shift occurs✓
4. DOnly PCl5 remains✓

Le Chatelier's principle can be applied to predict changes in equilibrium due to all of the following EXCEPT

1. AConcentration changes✓
2. BPressure/volume changes✓
3. CChanges in the amount of catalyst used✓
4. DTemperature changes✓

At chemical equilibrium, the Gibbs free energy of the system is

1. AMaximum✓
2. BAt a minimum✓
3. CIncreasing continuously✓
4. DEqual to enthalpy✓